The specific aims of this research are to investigate the biosynthesis, elaboration, secretion, and turnover of pulmonary surfactant, and to study these processes in terms of the ultrastructure of the alveolar lining layer and the cells pertinent to the synthesis and degradative events under normal, pathological, and experimental conditions. Morphological and biochemical systems to be studied are: a) Incorporation of various radioactively labeled precursors using radioautoggraphy;1. Alveolar lining layer turnover at a light and electron microscope level; 2. Intracellular pathway of label incorporation. b) Ultrastructure of the alveolar lining layer and of Type II cell lamellar bodies with freeze-etch technique: c) Cytochemistry of acyl transferase system especially with L-gamma C- glycerophosphate; d) Carbohydrate cytochemistry of the alveolar epithelial glycocalyx. Conditions under which these systems will be studied are: a) Normal, immature and adult; b) Gestation; c) Effects of thyroxine, pilocarpine, and Triton WR-1339; d) Hypoxia, simulated high altitude; e) Hyperoxia, 90-100% oxygen.